Commercial gas fired appliances, such as fryers, ranges and stoves, used in restaurants and other commercial and institutional kitchens, must be moved frequently to permit cleaning beneath and behind them as well as for enabling maintenance, repairs and inspections. Such appliances can weigh several hundred pounds and are equipped with casters to facilitate movement.
Connectors for delivering gas to commercial gas fired appliances have been constructed to permit movement without disconnecting the gas supply lines. One proposal was to construct the connector from lengths of rigid pipe connected together by relatively rotatable sealed swivel joints so that the pipe assembly was flexed and straightened and the appliance moved toward and away from its normal operating location.
Even though the pipe assemblies were capable of flexure during appliance movements the assemblies rigidly resisted movements in certain directions. When appliances turned during movement, bending and wrenching moments were exerted on the pipes and the swivel joints.
Flexible connectors have been proposed to enable turning the appliances while moving them to and away from their operating positions. Flexible connectors have been fashioned from flexible metal hoses and associated fittings for securing the hose ends to the appliances and the supply lines. Such connectors were flexed when the appliance was in its operating position and straightened out to permit moving the appliance from the operating position. The connectors were flexible enough to permit the appliance to turn or shift laterally relative to its operating position if desired.
Where the connector ends were rigidly fixed to the supply line and the appliance, tensioning the connector could damage the metal hose. Flexible metal hoses could be kinked and ruptured when the associated appliance was moved too far or too much force was applied. Kinking was a particular problem if an appliance was roughly pulled from its operating position to a location where the connector was taut and highly tensioned. Safety tethers were employed to limit the appliance travel from its normal location and prevent tautening the connectors, but tethers were not always effective.
A proposal has been made to provide triaxial swivel assemblies at the ends of the connectors. It was thought that these connector ends could be secured to the supply line and appliance in so that the hose could not kink. The theory was that the swivel assemblies would enable the opposite hose ends to align when the connector was straightened. U.S. Pat. No. 5,178,422 issued Jan. 12, 1993 discloses this proposal.
There were drawbacks to the '422 patent proposal. In the first place, the overall gas connector length is prescribed by industry regulations and includes the swivel assemblies. These assemblies were relatively long. Each included three separate members. To insure against kinking either hose end, a swivel assembly had to be placed at each connector end. Because the total swivel assembly length was great, the hose length had to be diminished proportionately.
The three axis swivel assemblies functioned relatively well except when all the axes in one, the other, or both swivel assemblies were substantially aligned in the same plane with the direction of applied hose force. Then the swivel assembly was unable to swivel (or "locked up") as the appliance moved away from its operating position. The normal position for each swivel assembly when the appliance was in its operating position was fully extended, hanging straight down with the hose positioned to pull in a generally horizontal direction. Conditions were thus ripe for swivel assembly lock up to occur.
During lock up, the swivel assembly was placed in bending stress as the applied hose force increased. The swivel assembly frictional forces resisting swiveling increased as hose force increased. Swivelling was even less likely to occur as appliance movement continued. Since the locked up swivel assemblies were long, the appliance could not reach its accustomed location when it was pulled out for cleaning.
The appliance could not move to its cleaning position even with the hose itself fully extended and in tension. Furthermore, because the locked up swivel assembly length was great, the safety tether could be slack when the hose was in tension. In these circumstances it was possible for cleaning personnel to try to force the appliance to its normal cleaning position, damaging the hose or a swivel assembly, or both.
Alignment of the swivel assembly axes with the hose pull direction did not occur every time the appliance was moved; but lock up did occur with sufficient frequency to create a problem. The swivel assembly rest position (illustrated in the '422 patent when the appliance was in the operating position) was with all the axes aligned. Moreover, because of swivel joint friction, the axes and hose pull direction did not have to be perfectly aligned for lock up to occur. This factor contributed to the lock up frequency.
Another shortcoming of the prior art proposals has been the tendency for connectors to experience torsional stresses when installed. The connector end fittings associated with the flexible metal hoses were constructed from threaded fittings hermetically welded to the hose ends. These fittings were attached to receptacles associated, respectively, with the appliance and the supply line. Installing such connectors between a supply line and an appliance created torsional hose stresses unless additional fittings, in the form of unions, were supplied to enable the connections. The unions had free turning nuts which enabled the fitting, union, and the supply line or the appliance to be attached together. When the fittings and unions were appropriately registered with each other the union nut was tightened. This precluded relative rotation between the hose end fitting and the union. Whenever the appliance was moved changes in one hose assembly end position relative to the opposite end created torsional stresses in the connector.
As a consequence, the connectors were required to be associated with a quick disconnect coupling, or equivalent relatively rotatable fitting, when used with a commercial gas appliance like a range or a fryer.
It was discovered that even when a quick disconnect or equivalent coupling was used to relieve torsional hose stresses, appliance movement to and away from the supply line location created stresses which were not dissipated. Whenever an appliance was moved away from the supply line at an angle other than normal to the wall behind the appliance, or when the appliance was turned as it moved, the connector end remote from the quick disconnect coupling was torsionally stressed as a result of movement. Under certain circumstances the torsional stresses tended toward kinking and damage to the hose assemblies.
The present invention provides a new and improved gas appliance connector wherein a flexible metal hose assembly and associated swivel fittings are constructed and arranged to maximize the hose length compared to the overall connector length, insure against swivel fitting lockup, attendant hose kinking and torsional stresses created by appliance movement, yet are uncomplicated and ruggedly constructed.